The present invention relates to a convenient process for the dehalogenation of aromatic and alpha-araliphatic halides which is simple, economic and eliminates the hazards of explosion and the like associated with the use of hydrogen gas or alkali metal alkoxides.
It is known, for example, in U.S. Pat. No. 4,337,368 to dehalogenate organic compounds, including polychlorinated biphenyl and chlorinated benzenes, with a reagent comprising polyethylene glycol, sodium and oxygen, presumably in the form of a sodium glycolate-superoxide complex, to form the corresponding hydroxylated biphenyls and phenols. An alternate technique is disclosed by Colebourne et al., Ger. Offen. No. 2,127,182, wherein chlorinated organics, including hexachlorobenzene, are reduced with gaseous hydrogen in the presence of platinum/aluminum oxide catalyst at elevated temperatures, specifically reciting 375.degree.. In Japanese Kokai No. 81.133,221, Chemical Abstract Vol. 96 No. 51959j, the dechlorination of 2-chlorotoluene is described with gaseous hydrogen under a pressure of 0.6 Kg/cm.sup.2 and an aqueous alkali metal hydroxide in the presence of palladium on carbon for over three hours at 70.degree..
The instant invention is based upon the discovery of a practical, economic process for the dehalogenation of aromatic and alpha-araliphatic halides in the presence of a hypophosphite salt and a hydrogenation catalyst in an aqueous or aqueous/organic or liquid alkanoic acid medium, preferably in the presence of a base.